1. Technical Field of the Invention
The present invention relates to communications systems and, in particular, to an architecture for providing both hardware and data redundancy to individual nodes in a communications system. The present invention is particularly applicable to providing such redundancy for system nodes utilizing data bases, for example, mobile telephone network home or visitor location registers.
2. Description of Related Art
The mobile switching center of a mobile telephone network includes a plurality of data bases which are consulted by the center during the establishment of a telephone connection within the mobile telephone network. These data bases include a home location register and a visitor location register which comprise platforms for storing in a data base format both static (i.e., non-changing) and dynamic (i.e., changing) data related to the subscribers.
The static data stored in the registers includes, for example, a list of identifiers for cooperating exchanges interconnected with the mobile switching center, an identification of the services (like transfer on busy) permitted for use by each subscriber, and the parameters associated with such services (like a fixed C number). The foregoing examples of data, as well as other types of static data, are entered into the data base and may be modified only by the administrator for the registers. The dynamic data on the other hand includes, for example, subscriber defined service data (like a variable C number), mobile station location data (with respect to both the mobile switching center and the base station), and mobile station activity data (like mobile station on/off status). This data, as well as other types of dynamic data, are entered into the data base and may be modified at any time by the subscriber, by the mobile station, or by the network in a manner that is transparent to the subscriber.
Because the home location register contains the data needed to establish a telephone connection within the mobile telephone network, the failure of the platform for the home location register will deprive a substantial number of subscribers of the capability of receiving or originating a telephone call. It is further important to remember that it is not only the platform, but also the static and dynamic data stored thereon, that are critical to the establishment of the telephone connection. Accordingly, there is a need for a system capable of handling a home location register platform failure from not only the hardware point of view, but also with respect to maintaining the integrity of the static and dynamic data stored thereon. Such a system will have applications in any data base system or communications system node wherein redundancy is required.